mm, hwpoison: cleanup some obsolete comments

1.Remove meaningless comment in kill_proc(). That doesn't tell anything.
2.Fix the wrong function name get_hwpoison_unless_zero(). It should be
get_page_unless_zero().
3.The gate keeper for free hwpoison page has moved to check_new_page().
Update the corresponding comment.

Link: https://lkml.kernel.org/r/20220830123604.25763-7-linmiaohe@huawei.comSigned-off-by: Miaohe Lin <linmiaohe@huawei.com>
Acked-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

mm/memory-failure.c

@@ -277,7 +277,7 @@ static int kill_proc(struct to_kill *tk, unsigned long pfn, int flags)
 		 * to SIG_IGN, but hopefully no one will do that?
 		 */
 		ret = send_sig_mceerr(BUS_MCEERR_AO, (void __user *)tk->addr,
-				      addr_lsb, t);  /* synchronous? */
+				      addr_lsb, t);
 	if (ret < 0)
 		pr_info("Error sending signal to %s:%d: %d\n",
 			t->comm, t->pid, ret);
@@ -1249,9 +1249,9 @@ static int __get_hwpoison_page(struct page *page, unsigned long flags)
 		return ret;
 
 	/*
-	 * This check prevents from calling get_hwpoison_unless_zero()
-	 * for any unsupported type of page in order to reduce the risk of
-	 * unexpected races caused by taking a page refcount.
+	 * This check prevents from calling get_page_unless_zero() for any
+	 * unsupported type of page in order to reduce the risk of unexpected
+	 * races caused by taking a page refcount.
 	 */
 	if (!HWPoisonHandlable(head, flags))
 		return -EBUSY;
@@ -2028,7 +2028,7 @@ int memory_failure(unsigned long pfn, int flags)
 	/*
 	 * We need/can do nothing about count=0 pages.
 	 * 1) it's a free page, and therefore in safe hand:
-	 *    prep_new_page() will be the gate keeper.
+	 *    check_new_page() will be the gate keeper.
 	 * 2) it's part of a non-compound high order page.
 	 *    Implies some kernel user: cannot stop them from
 	 *    R/W the page; let's pray that the page has been